AbstractCallback
	
abstract type defined in module 
	FluxTraining
			abstract type AbstractCallback
			Supertype of 
	
			
			SafeCallback/
			Callback. When implementing callbacks, you should subtype 
	
			
			SafeCallback instead.
The following pages link back here:
FluxTraining.jl , callbacks/callback.jl , callbackutils.jl , learner.jl